Research On Influence Factors And Regulatory Methods Of Sweep Coefficient And Displacement Efficiency Of SP Combination Flooding For Heavy Oil

Chemical flooding, as a substitute EOR technology after water flooding and polymer flooding for ordinary heavy oil, has been received extensive attention and has been proved to have excellent effect in pilot tests. At present, the surfactant/polymer binary flooding system has become the main research direction. In order to establish the formation of SP flooding system and investigate the displacement mechanism of Shengli heavy oil, hydrosulfobetaine with excellent interfacial activity has been synthesized in laboratory and compounded with HPAM to build combination systems with the same viscosity and different interfacial tension.The oil recoveries of different type flooding systems were evaluated by sandpack tests. The oil recovery, sweep coefficient and displacement efficiency were calculated by the means of microscopic displacement experiments and image analysis technology to illustrate the factors which controlling the enhanced oil recovery of heavy oil. The mechanisms of displacement were also proposed. The main conclusions and innovations are as follow:The ability to reduce the oil-water interfacial tension of hydrosulfobetaine was better than that of petroleum sulfonate surfactant. The adsorption quantity of hydrosulfobetaine/HPAM system on quartz sands was lower than that of petroleum sulfonate/HPAM system. The sandpack tests showed that the polymer flooding had good recovery effect on heavy oils and the recovery percent increases with the polymer concentration increasing. The economic concentration of polymer flooding is 0.15 wt%. A combination flooding system which obtains a higher recovery than polymer flooding was constituted by 0.01 wt% hydrosulfobetaine surfactant and 0.15 wt% HPAM. With the increasing of surfactant concentration the interfacial tension was reduced to ultra-low value.However, the recovery declines and was less than that of single polymer flooding. The sweep coefficient was the controlling factor of enhancing oil recovery of compounded system. The combination system with a low concentration of hydrosulfobetaine surfactant could obtain ahigher oil recovery. It can be explained by the dispersion of combination system was enhanced by low concentration of surfactant and the formation of W/O emulsions increased the percolating resistance of displacement phase in water passes. Then, the sweep coefficient was enlarged. The fingering between oil and rock clearance of combination system was enhanced by high concentration of surfactant, leading to a low sweep coefficient and enhanced oil recovery. The mixture of hydrosulfobetaine surfactants had a stronger intermolecular force and got enrichment status more quickly, which made for the production of instantaneous ultra-low interfacial tension. Therefore, the dispersion of binary compounded system in crude oil was promoted.